The present invention relates, in general, to non-volatile memory elements, and more particularly, to ferroelectric non-volatile registers.
Non-volatile configuration registers are commonly used for memory mapping and security purposes. These non-volatile registers can be implemented as stand alone registers or as part of a non-volatile memory array such as an electrical erasable programmable read only memory (EEPROM). An advantage of having the non-volatile registers as a portion of an EEPROM is the convenience it affords in realizing a long register. However, if the register is only a single byte in length, this technique becomes inefficient in terms of area, speed, and power. For example, access of non-volatile registers in an EEPROM requires a sense amplifier that needs to be activated. The sense amplifier consumes a large amount of power and occupies a large area on a semiconductor die. Further, the non-volatile register shares a highly capacitive bit line with a memory array. This capacitance slows down the access of the register and requires additional power for charging and discharging.
In addition, when implementing non-volatile registers in a memory array, a row of the memory array is normally used. As those skilled in the art are aware, a single row of the memory array typically consists of 128 or 256 bits, depending on the memory array structure. Since a register only requires a few bits, using a memory array structure to implement a register leaves a large number of bits of the memory array unused and, therefore, wastes a large portion of the memory array. This unused portion of the memory array consumes a large portion of the semiconductor die which is also wasted.
Accordingly, it would be advantageous to have a configuration register in which the registers are separate from the memory array structure. It would be of further advantage for the registers to be modular and capable of being cascaded to form memory blocks of different sizes. It is also desirable that accessing data in the register be simple, fast, and energy efficient.